Synopsis The Raytheon B300 (Super King Air) aircraft (registration C-GEJE, serial numberFL-385), operated by Grant Executive Jets Inc., was on a repositioning flight from Earlton to Timmins, Ontario, with only the flight crew and an engineer on board. At approximately 0650 eastern daylight time, the flight crew was conducting an instrument landing system (ILS) approach to Runway03 at Timmins. The autopilot was on and had been in use for the entire flight. The aircraft was in instrument meteorological conditions and icing conditions were encountered. The de-icing boots were being cycled and other anti-icing equipment had been selected ON. The aircraft was in level flight at 2700feet above sea level in the vicinity of the final approach fix, with the landing gear down and flaps selected to the approach setting. The aircraft was above the glide slope and the airspeed was approximately 100knots indicated airspeed (KIAS). The normal approach speed is approximately 125KIAS. The pilot flying (PF) began to take corrective action just as the aircraft stalled. The PF initiated a stall recovery by applying maximum power and lowering the aircraft's nose. Approximately 850feet was lost during the stall, and the aircraft reached a minimum height of approximately 800feet above ground level. Once the aircraft recovered from the stall, the crew flew a missed approach. The crew conducted another ILS approach at an approach airspeed of approximately 140KIAS and landed without further incident. After landing, the flight crew noted 1 to 1inches of ice on the aircraft's winglets and static wicks, and some ice on the engine nacelles and fuselage. Ce rapport est galement disponible en franais. 1.0 Factual Information 1.1 History of the Flight After take-off from Earlton, Ontario, the aircraft climbed to 10000 feet above sea level (asl)1 and after approximately 13minutes in cruise flight, the crew began a descent for the approach into Timmins, Ontario. The aircraft entered cloud at about 5000 to 6000feet asl and began to encounter light rime icing2 conditions. The remainder of the descent and approach, including the stall and stall recovery, were conducted in instrument meteorological conditions (IMC). Icing conditions intensified to moderate3 during the descent and approach. The flaps were selected to the approach setting in descent through approximately 4700feet asl. The aircraft proceeded directly to RIDIK, the global positioning system (GPS) initial fix for the instrument landing system (ILS) approach, approximately 10miles from the Timmins Airport (see AppendixA). The autopilot was in flight management system (FMS) mode and navigating to the selected GPS waypoint. After the aircraft started to accumulate ice during the descent, the captain, who was the pilot flying (PF), selected the wing and horizontal stabilizer de-ice boots ON approximately four times over a period of five minutes. The boots were functioning and were removing the ice from the leading edges of the wings. The flight crew could not determine if ice was being removed from the leading edges of the horizontal stabilizers because the horizontal stabilizers are not visible from the cockpit; however, the green annunciator lights were illuminating, indicating that those boots were inflating and deflating. There was no indication of ice accumulation on the upper surface of the wings. However, it was noted that ice was accumulating on the engine nacelles and on small sections of the inner leading edges of the wings not protected by de-ice boots. The aircraft levelled at 2700 feet asl in the vicinity of RIDIK. The autopilot was in altitude mode and maintained the selected altitude of 2700feet asl and in the FMS mode, steering the aircraft toward Sandy Falls, Ontario, the non-directional beacon (NDB) and next GPS waypoint. The ILS frequency was selected and the localizer and glide path were functioning, but the autopilot was not selected to Approach mode; therefore, it was not following ILS guidance. Just prior to Sandy Falls, four miles from the threshold of Runway03, the landing gear was selected down. The aircraft did not capture the glide path, but remained at 2700feet asl as commanded by the FMS and flown by the autopilot. The airspeed decreased to 98knots indicated airspeed (KIAS), and, at about 0653 eastern daylight time,4 the aircraft stalled without any pre-stall warning. The autopilot disengaged about two seconds after the stall. After completing a stall recovery and a missed approach, the flight crew conducted another ILS approach to Runway03 and landed successfully at 0707. 1.2 Flight Recorders The aircraft was equipped with an F1000 flight data recorder (FDR) manufactured by L3Communications. The FDR was shipped to the Transportation Safety Board of Canada (TSB) Engineering Laboratory for download and analysis of the data. Appendix B is a plot of the data at the time of the stall. The data show that the aircraft was level at 2700feet asl for approximately two minutes prior to the stall. After level off, the airspeed slowly decreased to about 135KIAS and then remained relatively constant for the next 30 seconds. The power was then reduced from 48percent torque to 20percent torque, resulting in a fairly rapid airspeed decrease to 98KIAS over the next 14seconds. Power was then increased to about 54percent torque and the aircraft began to roll left at a rate of about 5persecond. The airspeed held at 98KIAS for several seconds, while the roll rate increased to 15persecond and the pitch control position increased5 to +20 before the aircraft stalled. The autopilot remained engaged until the aircraft stalled. During the stall, the aircraft rolled left to 85 of bank and pitched to 39 nose down during a 0.25g pushover. Maximum power was applied and, as the airspeed increased rapidly above 125KIAS, a 2.4g pull-up was initiated. The back pressure was momentarily released while the aircraft was in a 30 nose-down attitude, allowing the aircraft to accelerate to 150KIAS before pulling to 2.7g. When the aircraft reached level flight, the back pressure was momentarily released before a 1.5g to 2g pull-up was initiated, with the aircraft reaching 30 nose up. The maximum allowable gload with flaps extended is 2.0g. The 30 nose-up attitude was held momentarily before it was adjusted to a normal climb attitude of 10 to 15. 1.3 Meteorological Information Prior to departing Earlton, the flight crew checked the en route and destination weather. There was no icing forecast in the graphic area forecast or the terminal aerodrome forecast (TAF) for Timmins. The hourly aviation routine weather reports (METARs) for Timmins and other nearby airports were not reporting any freezing precipitation or icing conditions. No pilot reports had been issued advising of icing conditions. The Graphic Area Forecasts for icing, turbulence and freezing level, issued at 0142 and valid for 0200 and 0800 on 22April 2004, depicted freezing levels from the surface to 5000feet. This indicated the possibility of warm air aloft, which when combined with below-freezing temperatures at the surface (as reported in the METARs), may be conducive to airborne icing conditions. Additional meteorological data are included in Appendix C. 1.4 Company Information Grant Executive Jets Inc. has an approved Air Operator Certificate (AOC) to operate three aircraft, two Falcons and one RaytheonB300 Super King Air (also known as King Air350). At the time of the occurrence, the company had recently acquired the King Air and it was being operated under Canadian Aviation Regulation (CAR)604, with a Canadian Business Aircraft Association Private Operator Certificate. Grant Executive Jets Inc. had intended to operate the King Air under CAR704 and applied to have the King Air added to its AOC as a 704aircraft. On 24June 2004, the aircraft was placed on the AOC under CAR703 because the company did not have a qualified line indoctrination training captain, as required under CAR704. 1.5 Personnel Information The captain held a valid Airline Transport Pilot Licence (ATPL) and was certified and qualified for the flight in accordance with existing regulations. He had accumulated 3500hours of multi-engine experience, 60hours of which was on the King Air350. On 15December 2003, he completed a surface contamination and airborne icing course. He completed the BE-300 (King Air350) initial pilot course at Flight Safety International (FSI) on 16January 2004. This included 28.5hours of flight simulator, 14.5hours of which were as the pilot not flying (PNF). One item on the 38-hour ground-training curriculum was crew resource management (CRM). He also completed the BE-300Collins Proline6 Differences Course at FSI, including 4hours of flight simulator on 31March 2004. The first officer also held a valid ATPL and was certified and qualified for the flight in accordance with existing regulations. Although he had almost 400hours on type, he had not flown the BE-300 for about three years. He completed the BE-350 Proline pilot initial course at FSI on 14April 2004. This included 14.3hours of flight simulator, all of which was conducted as the PF. He also received limited CRM training as part of the ground-training curriculum at FSI. On 15April 2004, he completed a surface contamination and airborne icing course. The occurrence flight was his first flight in C-GEJE since completing the training at FSI. 1.6 Flight Crew Preparation and Actions Preparations by the flight crew for the flight to Timmins were in keeping with normal company practices. The anticipated weather was IMC, but the ceiling and visibility were not expected to pose a problem or cause any delay in landing at Timmins. The captain briefed the approach in accordance with standard operating procedures (SOPs)7 but did not address issues such as minimum airspeed in icing conditions, the use of autopilot and flaps in icing conditions, or what to do in the event severe icing is encountered. He planned to fly a normal approach speed of 125KIAS. Chapter5, Section5.4, of the SOPs details the approach briefing that must be completed before every approach. The format for the approach briefing is the commonly used AMORTS.8 Under supplementary remarks, the SOPs list several items, including ice protection procedures and any special consideration or other relevant remarks. During the descent and approach, the flight crew never perceived the icing conditions to be severe9; however, conditions were described as moderate mixed10 icing. It was noted there was an abnormal accumulation of ice on certain parts of the engine nacelles, and toward the final approach segment, the icing was bordering on heavy. 1.7 Aircraft Information 1.7.1 General Records indicate that the aircraft was certified, equipped, and maintained in accordance with existing regulations and approved procedures. The weight and centre of gravity were within the prescribed limits, and the aircraft was certified for flight in known icing conditions. Compliance with ice protection was demonstrated in accordance with Federal Aviation Regulation23.1419, when ice protection equipment is installed in accordance with the equipment list. 1.7.2 Aircraft Ice Protection Systems The aircraft is equipped with electric windshield heat, an electric propeller de-ice system, and a pneumatic surface de-icing system that removes ice accumulation from the leading edges of the wings and horizontal stabilizers by alternately inflating and deflating the de-ice boots. All ice protection systems were serviceable and were functioning as designed. A three-position switch on the pilot's right subpanel, placarded Surface Deice - Single - Off - Manual, controls the pneumatic surface de-icing operation. The captain was operating the system in Single, which, when selected, opens a distributor valve to inflate the wing boots. After approximately six seconds, the wing boots are deflated and the horizontal stabilizer boots are inflated for four seconds and then deflated, completing the cycle. 1.7.3 Aircraft Stall Warning The stall warning system on the King Air 350 uses information from the lift transducer vane located on the leading edge of the left wing. The vane responds to the change in lift coefficient of the wing with a change in angle of attack and transmits a signal output to the lift computer. The computer processes signals from the lift transducer, flap position switch, landing gear squat switch and cockpit test switch. When the wing is not contaminated by ice accumulation, the system provides precise pre-stall warning by activating an aural warning when specific lift coefficients are reached. The system was not designed to account for aerodynamic degradation or adjust its warning to compensate for the reduced stall warning margin caused by ice accumulation. During certification trials with artificial ice shapes, it was determined that the aircraft demonstrated adequate pre-stall buffet. Ice protection for the stall warning lift transducer is provided by heating elements in the vane and mounting plate. The stall warning system was checked and found serviceable after the occurrence flight. The manufacturer's aircraft flight manual (AFM)11, Section5, Performance, indicates that the stall speed at the maximum weight with approach flaps and idle power is 88KIAS. The aircraft weight at the time of the occurrence was estimated at 13000pounds, or approximately 2000pounds below maximum gross weight. The AFM-calculated stall speed at this weight with flaps approach and idle power is 84KIAS. Due to the distortion of the wing airfoil, stalling airspeeds increase as a result of ice accumulation. A note accompanying the stall speed charts in the AFM states that, for operations with ice accumulation present, stall speeds may increase by nine knots. Stall warning devices may not be accurate with ice on the aircraft; therefore, when ice is present, the devices cannot be relied on. 1.7.4 Aircraft Operation in Icing Conditions When there is ice accumulation on the aircraft, it is necessary to maintain a comfortable margin of airspeed above the normal stall speed. Section2 of the AFM describes icing limitations. It states that the minimum airspeed for sustained icing flight is 140KIAS. Section2 also describes limitations when encountering severe icing conditions. Airworthiness Directive (AD)98-04-24,12 Operating in Severe Icing Conditions, required that specific text be incorporated into the AFM. Details of this text are provided in Appendix D. 1.8 Flight Crew Training 1.8.1 Flight Simulator Training The flight crew's simulator training at FSI included approach to the stall and stall recovery after the first indication of a stall. In-flight icing training at FSI consisted of limited exposure to icing conditions in the simulator during a normal departure sequence. 1.8.2 Crew Resource Management Training CRM training is a mandatory requirement for air operators under the Canadian Aviation Regulations (CARs), PartVII, Standard72513 (Airline Operations), but not for Standard724 (Commuter Operations). Commuter operations often involve the use of a two-person flight crew. Grant Executive Jets Inc. operates the RaytheonB300 using a crew concept, although the aircraft is certified for single-pilot operation. 1.8.3 Training in the Duties of Pilot Not Flying The initial pilot course at FSI does not include PNF roles and responsibilities in either the ground-training curriculum or the flight simulator sessions. Normally, trainees get bonus time in the right seat of the simulator, acting as the PNF for other trainees. When the first officer completed the BE-350 Proline pilot initial course, he did not act as the PNF during any of the simulator training because he was the only person on the course. The occurrence flight, his first flight in the aircraft, was the first time he acted as a PNF in the BE-350. He was familiar with PNF duties but had no previous opportunity to practise those duties. PNF duties are addressed throughout the company SOPs. Chapter5 provides detailed guidance on the arrival phase of flight and includes specific duties for both the PF and the PNF. For example, Section5.4, Approach Briefing, states (in part): During the actual approach, the flight crew is to compare the procedure as it is flown to what was briefed. Should a deviation become apparent to the PNF, it shall be brought to the attention of the PF. Section 5.10, Approach General, contains specific instructions regarding standard approach calls and clearly describes both PNF and PF responsibilities. For example, to reduce the likelihood of overshooting a desired track or vertical path during the intermediate/final approach phase, the PNF is instructed to warn the PF when approaching a track or ILS glide path. 1.9 Regulatory Guidance 1.9.1 Aircraft Stall Characteristics CARs, Part V, Airworthiness Standards 523.207, Stall Warning, applicable to commuter category aeroplanes, states that there must be a clear and distinctive stall warning, with flaps and landing gear in any normal position, in straight and turning flight. The warning must be provided to the pilot with sufficient margin to prevent inadvertent stalling. Airworthiness Manual Advisory (AMA)523/4A, dated 29October 1999, provides guidance material for acceptable means of demonstrating compliance with the flight characteristics requirements of Chapter 523, for the approval of commuter category aeroplanes for flight in icing conditions. The AMA states this advisory material is presently the subject of international harmonization, and this AMA is issued for use during type approval programs. When harmonization is completed, this AMA will be amended or revoked and the corresponding harmonized advisory material adopted. The procedures section of the AMA notes that approval of flight in icing conditions requires compliance with the following (in part): Flight characteristics with ice accumulations appropriate to 45minutes in Chapter525, AppendixC, conditions (3-inch maximum) on the unprotected surfaces and normally expected ice on the protected surfaces prior to anti-icing system operation or during system operation. The procedures section also lists items that have been found to be significant in past certification programs. Some of the items on the list include the following: the demonstration of adequate stall warning before stall characteristics; and the establishment of any systems limitations/procedures when operating in icing conditions (e.g. autopilot). While certification trials with artificial ice shapes determined that the aircraft demonstrated adequate pre-stall buffet, the flight crew of C-GEJE received no pre-stall warning horn and no noticeable buffet until in the stall. The aircraft stalled at 98KIAS, well above the calculated stall speed of 84KIAS with flaps approach and idle power, and significantly above 93KIAS, the estimated stall speed after adding the incremental 9knots for ice accumulation. 1.9.2 Pneumatic De-ice Boot Operating Procedures The Raytheon B300 AFM recommended procedure for the most effective de-icing operation is to allow at least 0.5inch of ice to form before boot activation. This procedure is aimed at maximizing the effectiveness of the pneumatic de-icing equipment by reducing the amount of residual ice and the possibility of ice bridging. Ice bridging, in which ice forms above the furthest extension of the boot tubes, occurred in older generation boots that were not powerful enough to completely shed ice. Modern de-ice boots, such as those installed on C-GEJE, are characterized by short-segmented, small-diameter tubes, which are operated at relatively high pressures and have relatively fast inflation and deflation cycles. Research since the mid-1990s found that modern de-icing boots are effective in both shedding ice and completely preventing ice bridging. Ice bridging is prevented because residual ice that is not shed after the initial boot cycle continues to increase in thickness and sheds during subsequent cycles. Transport Canada (TC) Commercial and Business Aviation issued Advisory Circular No.0130R on 15June 1999 to inform recipients of revisions to the airborne icing training guidance material. The guidance material was revised to include new information resulting from investigations into recent accidents in which airborne icing was determined to be a contributing factor. Air operators were informed that they were required to amend their training programs to include the new information before 01October 1999. The section Operational Use of Pneumatic De-Icing Boots states: Pilots of aeroplanes fitted with pneumatic de-icing boots will find direction on operational use of the boots in the AFM. In most cases the AFM will direct pilots to delay operation of the boots, either in the manual mode or automatic mode (if fitted), until to 1inch of ice has built up on the leading edge. As mentioned above, this guidance is almost universally included to prevent the occurrence of ice bridging. In its report on the fatal accident of a Comair EMB120 in January 1997, the National Transportation Safety Board (NTSB) of the United States concluded that a small amount of rough ice had built up on the wing as the aircraft slowed to configure for an approach, but this small amount was, however, sufficient to cause the aircraft to stall without warning as airspeed decreased. As a result, the NTSB recommends that, for modern turboprop aeroplanes: leading edge deicing boots should be activated as soon as the aeroplane enters icing conditions because ice bridging is not a concern in such aeroplanes and thin amounts of rough ice can be extremely hazardous. Unless specifically prohibited by the AFM, it is recommended that pilots of turbine-powered aeroplanes equipped with pneumatic de-icing boots with an automatic cycle, select the boots on automatic as soon as the aeroplane enters icing conditions. The boots should be left on until the aeroplane has departed the icing conditions. If the automatic boots have a FAST/SLOW option, the FAST option should be selected for moderate and severe icing conditions. The TC Advisory Circular made no mention of the operation of pneumatic de-ice boots on aircraft that do not have an automatic cycle, such as C-GEJE. 1.9.3 Use of Autopilot in Icing Conditions Autopilot use in icing conditions can mask the effects of airframe icing and possibly contribute to a loss of control. The autopilot may mask heavy control forces or trim the aircraft up to the point of stall and then disconnect unexpectedly with the aircraft on the brink of the stall. TC Advisory Circular0130R discusses monitoring the autopilot in icing conditions and states (in part) the following: It is highly recommended that pilots disengage the autopilot and hand fly the aircraft when operating in icing conditions. If this is not desirable for safety reasons, such as cockpit workload or single-pilot operations, pilots should monitor the autopilot closely. This can be accomplished by frequently disengaging the autopilot while holding the control wheel firmly. The pilot should then be able to feel any trim changes and be better able to assess the effect of any ice accumulation on the performance of the aeroplane. Section 1.21 of the company SOPs, on the use of the autopilot, states the following: Use of Autopilot: Crews are encouraged to make the maximum use of the aircraft autopilots. Whenever possible 'Coupled' approaches should be carried out subject to any restrictions in the AFM. An Autopilot ON/OFF call will be made by the PF and acknowledged by the PNF. 1.10 Additional Information 1.10.1 Aircraft Low Airspeed Warning Numerous accidents and incidents have occurred in which commercial flight crews failed to maintain adequate airspeed. The TSB and its predecessor, the Canadian Aviation Safety Board, have investigated at least eight accidents involving flight in icing conditions. In some cases, the failure to maintain airspeed resulted in catastrophic events such as loss of control and impact with terrain. The NTSB and other national accident investigation agencies have also investigated numerous events in which stall or failure to maintain airspeed was cited as a causal or contributing factor. Three such occurrences, in which safety issues similar to those involved in this occurrence were identified, are described in Appendix E. Past studies14 have noted that, when flight crews are monitoring automated systems, they may not be aware of the aircraft's energy state, particularly when approaching or trending toward a low-energy state. The studies indicate that flight crews need to be alerted before the aircraft reaches a potentially hazardous low-energy state. Advanced avionics capabilities may make it possible to develop and install low airspeed alert systems in many modern aircraft types. A low airspeed alert system has been developed for Embraer120 aircraft, and installation of the system was mandated by FAA AD2001-20-17. The system is designed to alert flight crews to low airspeed conditions in certain configurations and in icing conditions. Several avionics manufacturers offer low airspeed alert devices associated with approach and manoeuvring speeds, for use in less sophisticated general aviation aircraft. It may be feasible to develop low airspeed alert systems for most aeroplane types.